1. Field of the Invention
This invention relates generally to an apparatus for forming flexible tubular structures, and more particularly to an improved mandrel device to provide specific angular displacement for the respective mandrel rollers and their associated annular grooves.
2. Description of the Prior Art
It is well known in the art that various problems and difficulties are encountered in providing suitable means to form a continuous indefinite length of flexible tubing or ducting, particularly the type of tubing that is formed from an indefinite length of flexible ribbon-like material that must be wrapped about a continuous strand of wire as the ribbon and the wire are simultaneously wound about the rotating rollers of the mandrel.
Several machines and devices are used for forming such tubing so as to produce tubing or ducting in endless lengths. However, these known devices or apparatuses have features that either restrict their use so that they cannot produce a perfect uninterrupted continuous length of tubing, or they are so complicated to operate that they become prohibitively expensive to maintain.
It should be noted that the angular displacement of each mandrel is very critical. Thus, any movement of any one of the rollers will cause a mismatch between the moving ribbon and the associated wire that it must cover as the sealing takes place.
Flexible-tube manufacturing machines, such as the type disclosed in U.S. Pat. No. 3,778,327 to Fairchild (the inventor of the present apparatus), have been found to be workable--but with limitations as to output and diameter size.
In addition, machines known at this time do not provide sufficient structural support for their rollers to prevent angular misalignment of the respective rollers during prolonged operation. In this connection, an example of a tubing apparatus is disclosed in U.S. Pat. No. 4,012,272 wherein the rollers are adapted to be adjusted to produce various sizes of ducting. This arrangement, however, does not provide a substantial structural support to prevent misalignment of the rollers during use.
Accordingly, it has been found in the art that the angular displacement of the rollers and their associated annular grooves must be held in exact cooperating relationship to provide for a continuous production of tubing--particularly at high speeds. It has also been established that, in order to increase the diameter size of the tubing, not only does the angular displacement of the respective rollers change, but the number of rollers must increase or decrease according to the specific diameter. Ducting or tubing is made approximately from one inch in diameter to more than three feet in diameter. Thus, the machines as now designed have great difficulty in meeting such variations in size.